Why do I have stress incontinence when I'm only 26 and pregnant?

Common. Stress incontinence is common in pregnancy. There is a lot of pressure on the bladder from the growing uterus and baby and not much room for your other organs. This can lead to pressure on the bladder and leakage of urine. Follow up with a doctor if it continues past 12 weeks after giving birth.
The pregnancy. The baby can push the bladder down and fetal movements can exacerbate a weak bladder. I would recommend kegal's exercises, but this is a common complaint in pregnancy.